Heat treatment of copperberyllium alloys



Patented Oct 2, 1934 UNITED STATES PATENT OFFKZE HEAT TREATMENT OFCOPPER- BERYLLIUM ALLOYS Georg MaaingfBerlin, and Otto Dali], Berlin-Oharlottenburg, Germany No Drawing. Application mm 22, 1931,

Serial No. 1926 570,504. In Germany May 21,

11 Claims. (01. lie-:12)

This invention relates to improvements in heat 0 said method comprisingheating such a copperberyllium alloy to temperatures somewhat above atransition point lying at about 580 to 600 C., quenching and thereafterheating at temperatures below the-said transition point, say attemperatures from 150 to 500 C. for a time; said heating operationsbeing sometimes used individually and sometimes in the succession given,the choice depending on the specific alloy treated and the particularresults desired; all as more 0 fully hereinafter set forth and asclaimed.

In a prior and copending application, Serial No. 191,263, filed May 13,1927, of which the present application is a continuation in part, wehave described methods for heat treating copperberyllium alloys and theproperties of various alloys of this type; the alloys being specificallydescribed and claimed. In a. prior patent No. 1,685,570, we havedescribed and claimed processes for heat treating beryllium-nickelalloys in which nickel predominates. The present application is directedto copper-beryllium alloys of the type in which copper predominates andrelates particularly to methods for heat treating such alloys.

While various alloys of beryllium have been mentioned in the art, butlittle has been published concerning their properties. And it has beenfound that certain of these alloys have properties which makethemparticularly adapted for certain technical uses. Beryllium is one of thelightest metals employed technically and it is a good hardening agent inalloys. The hardness imparted to an alloy by the introduction of smallproportions of beryllium is characteristic. Cop per hardened by alloyingwithberyllium is a particularly useful material for technical purposes.By methods hereinafter-described certain properties of copper-berylliumalloys may be varied at will. For example the hardness may be increasedto that of hardened steel or reduced to a point at which the alloy maybe readily worked.

The copper-beryllium alloys with which the present invention is mostparticularly concerned have a beryllium content ranging from about 0.3up to 12 per cent; the residue. being copperor mainly copper. Thesealloys can be roughly divided into two ranges, according to theircharacteristics, (1) alloys from which a so-called beta modificationseparates from a melt and (2) alloys where the beta modificationdoes'not separate from a melt. It may be said that the beta modificationseparates upon solidification of alloys having, roughly, a berylliumcontent of from 5 to 12 per cent, while alloys having a lower content donot show such separation. The lower limit of the existence of the betamodification, however, is altered by the presence of other alloyingmaterials. Thus, in some instances, the beta modification has been foundto exist at compositions representing a beryllium content of as low as 3per cent, when other materials were present. 7 We have found that thesecopper-beryllium alloys may be hardened in a two-step process comprisingheating at an elevated temperature for some time, followed by quenchingand thereafter by age-hardening or tempering at a lower temperature fora time suflicient to improve their properties. But each step of thisprocess can also be employed alone to produce advantageous repoint and'the melting point, that is advantageously somewhat above 600 0.,followed by cooling. Small pieces cool withsufiicient rapidity in theair while large pieces should be quenched. This process is followed by aprolonged heating at temperatures below the transition point, such asfrom 150 to 500 C. This heating is continued for a time sufficient toimprove the properties of the alloys. At .the. lower temperaturesseveral days may be required for this treatment, while at 300," 0. twohours is suflicient. In a specific example of such a heat'treatment, analloy of 97 per cent. copper and 3 per cent beryllium, having an initialhardness of about 125 Brinell, was foundto have, 9. 817111811. f

Throughout the range of the existence of the beta modification the heattreatment required to produce the maximum hardness comprises merely thefirst step of the above described process,

namelyfa heating to temperatures above the final hardness of about 360m5 transition point followed by quenching. The sec-- ond step, namelyheating below the transition point may be advantageously employed toobtain the. alloy in agrelatively soft and mechanically workablecondition. In one case a copperberyllium alloy containing 6.7 per centof beryllium was found to have a hardness of 490 in the chilled casting.This hardness was increased to 730 by heat treatment above 580' 0.,followed by quenching.

Upon a subsequent prolonged heat treatment at temperatures below 580 C.the hardness of the above mentioned alloy was reduced to about 240Brinell. This latter treatment increases the duetility and toughness ofthe alloy. However, it may be worked readily while in this condition.

The above described heat treatments can be applied to both cast and tomechanically worked alloys. In the case of cast alloys the heattreatment at the higher temperatures may usually be obviated, thecooling in the casting taking the place of this treatment. A chilledcasting may be merely reheated between 150 and 300 C.

For the production of alloys having intermediate properties between theextremely hard and the workable types there are two methods available.The first method consists'in a heat treatment at intermediatetemperatures, for example between 450 and 800 C. Thesecond methodconsists of a prolonged heat treatment'at somewhat lower temperatures.This latter procedure is somewhat 'similar'to the final step of theusual two-step process. A preliminary mechanical.

working operation is frequently advantageous before the-heating step. i

The first efieet of a prolonged heating at temperatures below thetransition point is to harden the alloy, but this is followed by theproduction of high ductility and toughness as well as a high tensilestrength. Since the heating may be interrupted at any point, it ispossible in this way to produce alloys having, within'wide limits,almost any desired properties. Definite values of hardness, ductility,toughness and strength may be produced. Somewhat similar results to theabove may be obtained by heating the alloy above 600 C. followed by aslow cooling. This method is not as conveniently controlled, however.

In one particular example of the above heat treatment a copper-berylliumalloy, with a beryllium content of 2.5 per cent was heated at 500 C. forsome time. The alloy was then found to possess a notched bar toughnessof about 15 meterkilograms per square centimeter and a tensile strengthof kilograms per square millimeter. This same alloy, after being treatedby the twostepprocess, namely by heating above 600 C. and then at.temperatures in the neighborhood of 450 0., gave a notched bar testtoughness of only 1 meter-kilogram per square centimeter and was foundto have a tensile strength of 140 kilograms per square millimeter. -Ithas been found that advantageous results with'the above described singleheating at the lower temperatures are only obtained when theberylliumcontent of the alloy amounts to at least 1 per cent. a q

The effect of added bodies upon the'properties of the alloys and uponthe heat. treatments required is very striking. The addition of up to 1percent of phosphorus. has been foundto produce a considerable reductionin the amount of beryllium metal required to produce certain improved,characteristics. The time for aluminum and magnesium may be presentsimultaneously in the alloy with the production of improved properties.

A typical heat hardening process, as carried out with-an'alloy'containing 0.25 percent er phosphorus and about 1.5 per cent ofberyllium, may be carried out as follows: The alloy is heated above thepreviously mentioned transition point,

say at 800 C., and then quickly cooled. After cooling the hardness ofone particular sample was found to be..only Brinell. .By subsequentlytempering the alloy by heating for an hour at 350 0., the hardness wasincreased to 210 Brinell.

- In comparison with the above, when a copperberyllium alloy of the sameberyllium content but free from phosphorus was treated in the samemanner, the hardness, on cooling from 800 C.. was found to be 74 Brineliand, upon heating for as long as 7 hours .at 350 0., the hardnessincreased only 20 Brinell. The beneficial eilects of the phosphorusaddition is evident.

The beryllium content can be reduced without detrimentwhen additionmetals, such as aluminum, tin, silver and magnesium, are present in thealloy. Alloys of this type contain up to about 2.5 per cerit b1beryllium; a somewhat larger per beryllium. Since beryllium is by farthe most expensive of the metallic constituents, a reduction in thequantity required is advantageous. For

example, when copper only is alloyed with the beryllium at least 1 percent of beryllium must be present in order to give an alloy with a highdegree of hardness. But, upon theaddition of from 5 to 25 per cent ofoneoi the other metals mentioned, the beryllium content may be reduced toabout 0.3 per cent to obtain the same degree of hardness.

The heat treatment required for these multimetal alloys is similar tothat described previously. The two-step process is advantageous.

The properties of the above described copperberyllium alloys, includingwithin this term alloys which may contain one or more additional metals,fit them for many special technical uses. The alloys are especiallysuited for making metallic springs, whether of leaf, helical or spiralform. The use of such springs in instruments of precision is highlyadvantageous due to their high resistance to corrosion and permanentcharacteristics. The use of the described alloys in electricalinstruments is desirable, especially where there is frictional contact,for example in knife switches, commutators, slip rings, bearings,sliding contact points, etc.

By the terms remainder substantially copper" and "balance substantiallycopper, occurring in the claims, we mean that the alloys called for mayalso contain small amounts of addition metals acting to reinforce thehardening eflect of the beryllium, these metals, including phosphorus,tin, zinc, iron, cobalt and aluminum occurring in amounts insuiilcientto substantially alter the characteristic properties or the said alloys.

What we claim is:

1. In the heat treatment of copper-beryllium alloys containing fromabout 0.3 to 12 per cent by weight of beryllium with the remaindersubstantially copper, the process which comprises heating such an alloyat temperatures above a transition point, which lies in the neighborhoodof 580 to 600 C., but below its melting point, quenching andage-hardening by prolonged heating at temperatures above about 150 C.but below said transition point.

2. In the heat treatment of copper-beryllium alloys containing fromabout 0.3 to 12 per cent by weight of beryllium with the remaindersubstantially copper, the steps which comprise heating such an alloy attemperatures below its melting point but above about 580 C. andsubsequently quenching.

3. In the heat treatment of copper-beryllium alloys containing fromabout 0.3 to 12 per cent by weight of beryllium with the remaindersubstantially copper, the step which comprises tempering such an alloyby a prolonged heating at temperatures below about 580 to 600 C. butabove about 150 C.

4. The process of heat treating copper-beryllium alloys having aberyllium content above about 0.3 per cent but below percentages atwhich the beta-modification separates upon solidification, ranging fromabout 3 to 5 per cent by weight, with a balance substantially copper,which comprises heating such an alloy at temperatures below its meltingpoint but above about 600 C., and age-hardening by heating attemperatures ranging from about 150 to 500 C. until its physicalproperties have been improved.

5. In the heat treatment of copper-beryllium alloys containingsuflicient beryllium to cause separation of the beta-modification uponsolidification, ranging from about 3 per cent to 12 per cent by weight,with a balance substantially copper, the process which comprises heatingsuch an alloy at temperatures below its melting point but above about600 C.- and quenching.

6. The process of claim 5 in which the alloy is further heated attemperatures between 150 to 500 C. in order to produce workableproperties.

7. In the heat treatment of copper-beryllium alloys containing from 0.3to 12 per cent by weight of beryllium, with a balance substantiallycopper, the process which comprises heating such an alloy for aprolonged interval at temperatures between about 150-600 C. to producehigh ductility and toughness.

8. The process of claim '7 wherein the heating step is preceded with amechanical working operation.

9. The process of claim 3 in which the temperature of the tempering steplies between 150 and 500 C.

10. In the heat treatment of copper-beryllium alloys containing fromabout 0.3 to 12 per cent by weight of beryllium with a balancesubstantially copper, the process which comprises chillcasting such analloy and reheating to temperatures between 150 and 500 C. untilthephysical properties have been improved.

11. The process of claim 1 wherein the copperberyllium alloy alsocontains from about 0.1 to 1 per cent of phosphorus.

12. The process of claim 2 wherein the copper-beryllium alloy alsocontains from about 0.1 to 1 per cent of phosphorus.

13. The process of claim 3 wherein the copperberyllium alloy alsocontains from about 0.1 to' 1 per cent of phosphorus.

14. The process of claim 4 wherein the copper-beryllium alloy alsocontains from about 0.1 to 1 per cent of phosphorus.

15. The process of claim 5 wherein the copperno beryllium alloy alsocontains from about 0.1 to 1 per cent of phosphorus.

16. The process of claim 7 wherein the copperberyllium alloy alsocontains from about 0.1 to 1 per cent of phosphorus. 115

17. The process of claim 10 wherein the copper-beryllium alloy alsocontains from about 0.1

to 1 per cent of phosphorus.

GEORG MASING. OTTO DAHL.

